(1) Field of the Invention
The present invention generally relates to a fiber-detachable-type optical module, and more particularly to an optical module, including an optical device, in which an optical fiber connected thereto is detachable therefrom.
(2) Description of the Related Art
An optical module is provided with an optical fiber, an optical semiconductor device and a printed circuit board on which circuitry processing electric signals is formed. The optical semiconductor device may include a laser diode (LD) for converting electric signals into optical signals and a photo diode (PD) for converting optical signals into electric signals. The optical module is employed for optical communication (optical transmission and/or reception).
In a process for soldering pins of the circuit board of the optical module on a board, a flow-soldering method is advantageous in that the number of working steps can be reduced. However, since the optical fiber is covered with a high polymer weak in heat, such as polyethylene, the flow-soldering method cannot be used for the optical module to which the optical fiber is connected.
Thus, the flow-soldering method is applied to the optical module under a condition in which the optical fiber is detached from the optical module. After the optical module is soldered on a board by using the flow-soldering method, the optical fiber is connected to the optical module.
The optical module from which the optical fiber can be detached as described above is referred to as a fiber-detachable-type optical module.
A conventional fiber-detachable-type optical module is formed as shown in FIGS. 1A and 1B.
Referring to FIG. 1A, an optical module is provided with a module body 3 and optical fibers 2. A printed circuit board 4 is mounted in the module body 3. The printed circuit board 4 has lead pins 5 through which signals are output from and input to the printed circuit board 4 and electric power is supplied to the printed circuit board 4. Optical elements 6A such as the laser diode (LD) and the photo diode (PD) are mounted in the module body 3.
Each of the optical fibers 2 is provided with optical connectors 8 and 9 at respective ends. One optical connector 8 is connected to the module body 3 so that optical signals travel between the optical fiber 2 and the optical element 6A through the optical connector 8. The other optical connector 9 of each of the optical fiber 2 is connected to an external unit so that optical signals travel between the optical fiber 2 and the external unit through the optical connector 9.
FIG. 1B shows internal structures of the module body 3 and the optical connector 8 of the optical fiber 2.
Referring to FIG. 1B, in the module body 3, the printed circuit board 4 is fixed and an optical device 6 including one of the optical elements 6A is rigidly fixed by means of potting 10 (or molding). Lead terminals of the optical device 6 are soldered on the printed circuit board 4. The optical device 6 is connected with a ferrule 12 supporting an end portion of an optical fiber coupled to the optical device 6.
The optical connector 8 has a ferrule 13 supporting an end portion of the optical fiber 2. An insertion portion 14 through which the ferrule 13 freely passes is inserted in and engaged with an engaging portion 15 of the module body 3, so that the ends of the ferrules 12 and 13 are in rigid contact with each other. The optical device 6 transmits and receives optical signals to and from the optical fiber 2 via the ferrules 12 and 13.
The ferrule 13 of the optical connector 8 is elastically supported by a spring 16 in a direction in which the ferrule 13 extends. As a result, when the optical connector 8 is connected to the module body 3, an impact stress generated in the ferrules 12 and 13 is softened. Thus, the end surfaces of the respective ferrules 12 and 13 are prevented from being broken by the impact stress.
However, for example, in cases of assembling the optical module 1, testing the optical module 1 and the like, after the optical fiber 2 is connected to the module body 3, the optical fiber 2 may be pulled. At this time, due to the repulsion of the spring 16 elastically supporting the ferrule 13 of the optical connector 8, the ferrule 13 may come into collision with the ferrule 12 in the module body 3 with a large impact. If the collision between the ferrules 12 and 13 is repeated, the end surface of the optical fiber 2 may be damaged, so that the optical transmission loss is increased and a state in which light is reflected on the end surface of the optical fiber 2 is changed.